snapshot of random sampling (127M out of 400M txns):

Snapshot_4bytes

Count        Signature     %        % (without 0x)  Function
222,852,719  0x            55.96%            ETH TRANSFER
87,649,468   0xa9059cbb    22.01%   49.97%   transfer(address,uint256) OR many_msg_babbage(bytes1)
4,265,659    0x0a19b14a    1.07%    2.43%    trade(address,uint256,address,uint256,uint256,uint256,address,uint8,bytes32,bytes32,uint256)
3,935,612    0x6ea056a9    0.99%    2.24%    sweep(address,uint256)
3,297,997    0xef343588    0.83%    1.88%    trade(uint256[8],address[4],uint8[2],bytes32[4])
3,247,646    0x0f2c9329    0.82%    1.85%    split(address,address)
2,960,633    0x095ea7b3    0.74%    1.69%    approve(address,uint256)
2,476,038    0x00000000    0.62%    1.41%    -
2,470,649    0xa9b1d507    0.62%    1.41%    makeWallet()
2,469,748    0xd0e30db0    0.62%    1.41%    deposit()
2,069,616    0x278b8c0e    0.52%    1.18%    cancelOrder(address,uint256,address,uint256,uint256,uint256,uint8,bytes32,bytes32)
1,956,239    0x60606040    0.49%    1.12%    ?
1,930,489    0x338b5dea    0.48%    1.10%    depositToken(address,uint256)
1,591,100    0x42c8705b    0.40%    0.91%    Mine()
1,476,551    0x9e281a98    0.37%    0.84%    withdrawToken(address,uint256)
1,391,026    0xf7d8c883    0.35%    0.79%    breedWithAuto(uint256,uint256)
1,369,808    0x00          0.34%    0.78%    -
1,368,324    0xf7654176    0.34%    0.78%    split()
1,257,261    0x2e1a7d4d    0.32%    0.72%    withdraw(uint256)
1,211,277    0x2295115b    0.30%    0.69%    adminWithdraw(address,uint256,address,uint256,uint8,bytes32,bytes32,uint256)